Please note that we’ve uploaded new macOS builds. The previous ones only supported macOS 10.15+ (Catalina). The new ones support 10.13+ (High Sierra, Mojave, Catalina, and any upcoming macOS release).
Also note that you may get the following message when loading/saving OGR files (eg, Shapefiles) with pyGPlates (although if you happen to have the PROJ library installed on your system then you might not):
ERROR 1: PROJ: proj_identify: Cannot find proj.db
ERROR 1: PROJ: proj_create_from_database: Cannot find proj.db
…but the proj.db file should not be needed by pyGPlates, so you can ignore the error for now. We are addressing this issue in the next GPlates/pyGPlates releases.